The invention relates to a displacer unit having at least one displacer space which is arranged in a cylindrical drum rotating about an axis of rotation and which can be connected to an inlet connection and an outlet connection by means of a control surface, wherein the control surface is formed on a valve plate body which is provided with a first control opening, which is connected to the inlet connection, and with a second control opening, which is connected to the outlet connection.
With generic displacer units, which can be operated as compressors or motors, the alternating connection of the displacer spaces arranged in the rotating cylindrical drum is guaranteed with the inlet opening and outlet connection embodied on the housing by means of the control surface. The control surface is embodied on a valve plate body, which is provided with a kidney-shaped control opening that is connected to the inlet opening, and a kidney-shaped control opening that is connected to the outlet connection. The control openings in this case are arranged on a common divided circle.
The rotating cylindrical drum in this case is adjacent to the stationary valve plate body, whereby each displacer space has a connecting opening for connection to the control openings. A flat seal is provided between the connecting opening and the control openings.
In the case of these types of displacer units, hydrostatic relief is provided to reduce the friction that arises on the flat seal. The hydrostatic relief, however, produces leakage flows between the inlet side and the outlet side, as well as from the inlet side and from the outlet side to the housing interior. In addition, a pressure medium flow occurs between the displacer spaces. The flat seal continues to show evidence of increased leakage flow already with slight damage or wear. Because of these leakage flows, operation of the displacer unit is restricted to a specific maximum operating pressure. Generic displacer units are therefore not suited for operating the displacer unit at high maximum operating pressures, in particular pressures of up to 1000 bar, because of the increasing leakage flows and the associated poor efficiency.
The present invention is based on the objective of making available a displacer unit of the species cited at the outset, which has low leakage flows and therefore is suitable for operation at high maximum operating pressures.
This objective is attained in accordance with the invention in that the first control opening and the second control opening are spaced apart radially, wherein the displacer space can be connected to the first control opening by means of a first connecting passage and to the second control opening by means of a second connecting passage, and the connecting passages are provided by means of a respective mechanical face seal for sealing relative to the control opening. According to the invention, the control openings of the valve plate body are thus arranged on separate divided circles and the displacer space can be connected to the corresponding control opening by means of two connecting passages arranged on separate divided circles, wherein the displacer spaces are sealed by means of the mechanical face seals instead of a flat, prior art seal. This type of seal, using mechanical face seals, makes it possible to effectively avoid leakage flows between the displacer spaces and leakage flows between the inlet side and the outlet side, as well as from the inlet side and the outlet side to the housing interior. The inventive displacer unit is thereby suited for operation at high maximum operating pressures of in particular up to 1000 bar, and has a high efficiency in this case.
According to a preferred embodiment of the invention, the mechanical face seal is embodied as a mechanical face bushing. By using annular mechanical face bushings, it is possible to seal the connecting passages of the displacer spaces in a simple manner relative to the control openings arranged in the valve plate body.
The mechanical face seal can be acted upon with special advantage by means of a spring in the direction of the valve plate body. The mechanical face seals embodied as mechanical face bushings are thus pretensioned by the spring and are pressed on the control surface by the spring. This allows a secure abutment of the mechanical face bushing on the valve plate body—and thus a secure seal—to be achieved.
According to a preferred development of the connection, the mechanical face seals are provided with a control surface acting in the valve plate body direction, wherein the control surface can be acted upon by the pressure available in the connecting passage. This allows the pressure available in the displacer space to also act on the mechanical face seals embodied as mechanical face bushings, and thus the mechanical face bushings, to act on the control openings as a function of the available operating pressure so that, when operating the displacer unit at high operating pressures, a secure seal of the displacer spaces relative to the control openings is achieved resulting in low leakage flows.
A simple structure with low manufacturing expenses can be achieved with the connecting passages provided with mechanical face seals, if the mechanical face seal is arranged in a bore-shaped recess of the connecting passage.
A preferred embodiment of the invention provides that the mechanical face seals are sealed relative to the recess by means of an O-ring. This allows a leakage flow between the recess and the mechanical face bushing to be prevented effectively and with low construction expense.
Particular advantages are produced if, according to a development of the invention, a sealing device is provided for sealing the first control opening relative to the second control opening and/or a sealing device for sealing the first control opening relative to a housing interior and/or a sealing device for sealing the second control opening relative to the housing interior. These types of sealing devices make it possible in a simple way to seal the first control opening relative to the second control opening as well as to seal the first control opening and the second control opening relative to the housing interior and thus to seal the control openings, thereby preventing leakage flows between the control openings and from the control openings to the housing interior, therefore making it possible to operate the displacer unit at high operating pressures and with high efficiency.
In this case, the sealing device is embodied as a mechanical face seal according to a preferred embodiment. The control openings can be sealed in a simple manner with these types of annular mechanical face seals.
If the sealing device, in accordance with an expedient development of the invention, can be acted upon by means of a spring in the direction of the cylindrical drum, it is possible to achieve a secure abutment of the sealing devices embodied as mechanical face seals on the cylindrical drum in order to seal the control openings.
Special advantages are produced if the sealing devices are provided with a control surface acting in the direction of the cylindrical drum. This produces pressure-dependent pressing on the sealing devices embodied as mechanical face seals so that, when operating the displacer unit at high pressures, a secure seal of the control openings among each other and relative to the housing interior is achieved, and therefore, low leakages.
According to a preferred embodiment of the invention, the control surface of the sealing device that seals the first control opening relative to the second control opening, and the control surface of the sealing device that seals the second control opening relative to the housing interior, can be acted upon by the pressure available in the second control opening, and the control surface of the sealing device that seals the first control opening relative to the housing interior can be acted upon by the pressure available in the first control opening. In the case of a displacer unit that is operated as a compressor, in which the first control opening is connected to the inlet opening that is acted upon with low pressure and the second control opening is connected to the outlet connection maintaining the maximum operating pressure, low pressure additionally acts on the sealing device that seals the first control opening relative to the housing interior, and the operating pressure available in the second control opening additionally acts on the sealing device that seals the first control opening relative to the second control opening as well as the sealing device that seals the second control opening relative to the housing interior, thereby achieving a secure seal of the first control opening and the second control opening.
A simple arrangement of the sealing device embodied as mechanical face seals can be achieved with low construction expense if the sealing devices are arranged in an annular free space of the valve plate body.
Leakage flows between the free spaces and the sealing devices can be avoided in a simple way if the sealing device—according to an expedient development of the invention—is sealed relative to the free space by means of an O-ring.
The control openings in this case are embodied expediently as kidney-shaped control openings.
If, according to an advantageous development of the invention, the valve plate body can be rotated relative to the axis of rotation by means of a regulating device, in particular a control piston, it is possible in a simple manner to change the engagement time points of the control openings, and in particular the control opening that is acted upon, with the maximum operating pressure. As a result of this, pressure equalization flows and pressure pulsations, which occur when connecting the displacer space to the control opening maintaining the maximum operating pressure due to the difference in pressure between the displacer space and the pressure available in the control opening, are reduced; whereby, in the case of a displacer unit operated as a compressor, pressure pulsations and pressure equalization flows, which allow the energy consumption of a displacer unit operated as a compressor to rise, can be reduced and avoided.
The displacer unit can be operated as a compressor or as a motor and is suited for operation with liquids as well as with gaseous media, particularly hydrogen.